1. Field of the Invention
A certain kind of virus carries a component called HA antigen (Hemagglutination Antigen), which has a property agglutinating the animal erythrocytes, on their particle surface. Anti-virus antibodies inhibit the agglutination between the HA antigens and the animal erythrocytes. An anti-virus antibody titer can be determined by the Hemagglutination Inhibition (HI) test utilizing such a property of HA antigen.
Of the clinical tests for various viruses, the most general one is determination of antibody titer against rubella virus; and the HI test is generally used as serological method for diagnosing an infection or anamnetic infection with rubella virus. Particularly, rubella infection in the first pregnant stage is a matter of primary concern for pregnant women in a delivery stage as it causes a birth of congenital rubella child, so that the rubella HI antibody titer test has widely been applied as one of screening tests for pregnant women.
This invention relates to a method for stabilizing rubella HA antigen which is used in the rubella HI test based on the hemagglutination inhibition.
2. Prior Art
Rubella HA antigen is used in the rubella HI antibody titer test practiced generally. Rubella HA antigen suspension is desired to be stable without deterioration of antigen titer over a long term for simplifying a titer-adjusting procedure at the time of use and also for securing reproducibility of the data and accuracy of the test. And the stabilization prevents the waste of the reagent especially in dealing with a small number of samples. Therefore, various methods for keeping rubella HA antigen stable have been studied. For example, P. E. Halonen reported that rubella HA antigen which was extracted from the cells infected by rubella virus with a glycine buffer (pH 9.0) was stable at 4.degree. C. and -70.degree. C. for a few weeks. [Proc. Soc. Exp. Biol. Med. 125, 162-167 (1967)]. It is advertised that commercially available rubella HA antigen (by Flow Co.) is stable at pH 9.0-9.5 at 4.degree. C. for 24 hours, but unstable at the lower pH range. Addition of sodium azide as a sterilizer at a concentration of about 0.1% is also effective.